A Saudi-led military coalition mounted air strikes on Yemen's Houthi-controlled capital Sanaa on Sunday after it intercepted 10 drones launched by the Iran-backed rebels, state media reported.
"The military operation targets Houthi military capabilities in Sanaa and a number of other provinces," the coalition was quoted as saying by the official Saudi Press Agency.
The strikes triggered huge explosions in Sanaa and sent plumes of smoke rising in the sky, according to an AFP correspondent and photographer at the scene. The rebels reported seven air strikes on Sanaa.
The raids come after the coalition said it intercepted 10 drones launched by the rebels on Sunday, in a sharp escalation in cross-border attacks on the kingdom.
The coalition -- fighting in Yemen alongside the internationally recognised government against the insurgents -- said the drones were aimed at "civilian" targets in Saudi Arabia, SPA reported, without specifying the locations.
Targeting civilians in the kingdom was a "red line", the coalition said after the retaliatory strikes on Sanaa.
The rebels did not immediately claim responsibility for the drone attacks
The Houthis have stepped up attacks on Saudi Arabia in recent weeks, while they escalate an offensive in Yemen to seize the government's last northern stronghold of Marib.
The escalation comes even after the United States last month delisted the Houthis as terrorists and stepped up efforts to de-escalate the six-year conflict.
The terror designation, imposed late in the administration of former US president Donald Trump, had been widely criticised by aid organisations, who warned it would hamper their efforts to alleviate a humanitarian crisis in Yemen.
"The removal of the Houthis from the list of terrorist groups has been interpreted in a hostile way by the militia," SPA cited the coalition as saying.
The coalition added that their "victories" in Marib had prompted the rebels to step up attacks on the kingdom.
On Saturday, Yemeni government sources said fierce fighting between pro-government forces and the rebels in oil-rich Marib had left at least 90 combatants on the two sides dead over the span of 24 hours.
Years of bombing have failed to shake the rebels' hold on Sanaa, and they have steadily expanded their reach in the country's north.
US President Joe Biden halted support to Saudi offensive operations in Yemen's war, which he called a "catastrophe" that "has to end".
But he also reiterated US support for Saudi Arabia in defending its territory.
The grinding conflict has claimed tens of thousands of lives and displaced millions, according to international organisations, sparking what the UN calls the world's worst humanitarian crisis.